Liquid crystal display devices control transmission/shielding of light (ON/OFF of display) by controlling the alignment of birefringent liquid crystal molecules. Exemplary liquid crystal alignment modes of liquid crystal display devices include a twisted nematic (TN) mode in which liquid crystal molecules having positive anisotropy of dielectric constant aligned are twisted 90° when seen in the normal direction of a substrate, a vertical alignment (VA) mode in which liquid crystal molecules having negative anisotropy of dielectric constant are aligned in a direction perpendicular to a substrate surface, and an In-Plane Switching (IPS) mode and an FFS mode in which liquid crystal molecules having positive or negative anisotropy of dielectric constant are aligned in parallel with a substrate surface, and a transverse electric field is applied to a liquid crystal layer.
A popular driving method of liquid crystal display devices is an active-matrix driving method in which an active element such as a thin film transistor (TFT) is provided in each pixel to realize high-definition images. In an array substrate provided with a plurality of TFTs and a plurality of pixel electrodes, a plurality of scanning signal lines and a plurality of data signal lines are formed to cross each other, and the TFTs are provided for respective intersections. The TFTs are connected to the pixel electrodes and control whether or not to supply an image signal to the pixel electrodes by their switching functions. An array substrate or a counter substrate further includes a common electrode to apply a voltage inside a liquid crystal layer through a pair of electrodes.
Among the modes for controlling the alignment of liquid crystal molecules by applying a transverse electric field, the FFS mode is a liquid crystal alignment mode in which one substrate includes a first electrode and a second electrode and an insulating film is provided between the first electrode and the second electrode (see Patent Literature 1). The first electrode and the second electrode are formed of a light-transmitting conductive material such as indium tin oxide (ITO) and indium zinc oxide (IZO). One of the first electrode and the second electrode is connected to a common wiring and the other is connected to a TFT. The electrode connected to a TFT includes a plurality of slits formed therein. Providing such a pair of electrodes enables to generate a fringe electric field in a manner as to pass through the slits between the first electrode and the second electrode, thereby enabling to control the alignment of liquid crystals. According to Patent Literature 1, the shape of the electrode in which the slits are formed and the shape of the slits are adjusted so as not to cause disclination in liquid crystals.